1. Field of the Invention
The present invention relates to an image recording apparatus in which recording media, such as recording paper sheets, can be reliably supplied by suction to the transfer mechanism.
2. Description of the Related Art
Ink-jet printers have hither to known as image recording apparatuses. Any ink-jet printer has a recording head that has a plurality of nozzles, from which ink droplets are ejected, recording a high-quality image at high speed on a recording medium being transferred by a transfer mechanism. The ink-jet printer has a transfer belt as the transfer mechanism. The transfer belt has a plurality of suction holes. Any ink-jet printer that has a transfer belt comprises a suction unit in most cases. The suction unit draws air through each suction hole of the transfer belt. The suction unit has, for example, a suction fan. The transfer mechanism holds the recording medium on the transfer belt by action, as the suction unit draws air.
While the ink-jet printer is recording (or printing) an image, ink droplets are formed, or ink mist is generated. Therefore, the ink droplets or ink mist may stick to the transfer belt as the ink droplets or ink mist is drawn in the system wherein air is drawn to attract the recording medium to the transfer belt. The ink droplets or ink mist, if any on the transfer belt, may stick to the reverse side of the recording medium, possibly making the recording medium dirty.
An ink-jet printer of the type described above may use the technique of automatically closing those of the suction holes, which are not closed with a recording medium placed on the transfer belt, in order to prevent the medium from becoming dirty with ink droplets or ink mist, to prevent the suction force applied on the recording medium from decreasing due to an in-flow of unnecessary air, and to prevent power consumption of the suction fan.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2003-159841 discloses the technique of automatically opening and closing the valves provided in suction holes. The suction plate has a plurality of suction holes. In each suction hole, a valve is provided, which can open and close in accordance with changes in the amount of air applied by a suction fan. In any suction hole made in that region of the suction plate, which does not contact a paper sheet, air flows in a large amount, closing the valve provided in the suction hole.
Jpn. Pat. Appln. KOKAI Publication No. 5-35022 discloses the technique of opening and closing suction holes with spherical bodies. The drum has a plurality of suction holes. In each suction hole, a movable spherical body is provided. The paper sheet is attracted by suction to any suction hole that is covered with the paper sheet, because the spherical body does not plug the suction hole. In any suction hole that is not covered with the paper sheet, the spherical body plugs the hole, not allowing air to flow through the suction hole.
Jpn. Pat. Appln. KOKAI Publication No. 5-131692 discloses the technique of opening and closing suction holes by using valves. A platen has a plurality of suction holes. Each suction hole has a valve, which has a spring. Each valve automatically opens or closes in accordance with the amount of air flowing through the suction hole. Any suction hole that is not covered with a paper sheet is closed by the valve because air flows in a large amount in the suction hole. Any suction hole that is covered with a paper sheet is opened by the valve because air flows in a small amount in the suction hole.